This presentation is a three-dimensional analysis of first-tarsometatarsal joint after first-tarsometatarsal osteotomy with weight-bearing CT. The pathology of bunion deformity consists of deformities in the axial, coronal, and sagittal planes of a first-tarsometatarsal and its articular surface with the medial cuneiform. While weight-bearing radiographs have been utilized for assessment of these deformities, these methods have limitations in regard to their image magnification, patient position, and superimposition of bone alignments. With the advancement of weight-bearing CT, evaluation of three-dimensional components of first-tarsometatarsal along with its proximal articular surface can be assessed with greater precision. The purpose of this study is to observe the effects of mid-shaft osteotomy on the alignment of the tarsometatarsal joint in three dimensions. We looked at 10 categoric specimens that underwent mid-shaft first-tarsometatarsal osteotomies. We took pre- and post-operative weight-bearing CT scans with 0.3 mm3 voxel size were collected from each of the subjects in neutral standing position. 3D models were rendered of the medial cuneiform, first-tarsometatarsal, and the great toe, which were generated from the scans followed by a definition of the reference frames for each bone to evaluate the changes of the metatarsal in relationship to the medial cuneiform. Once this was completed, the measurements of the rotation parameters of our study showed greater changes in the coronal plane post-operatively with eversion of the first-tarsometatarsal relative to the medial cuneiform. Post-operative changes in the sagittal plane and axial plane with relationship of the first-tarsometatarsal to the medial cuneiform were not statistically significant. Distance mapping showed a significant increase in surface-to-surface distance at the dorsal-tarsometatarsal joint post-operatively with reduced distance at the inferior portion of the tarsometatarsal joint. Based on the results of this study, mid-shaft osteotomies of the first-tarsometatarsal can cause increased dorsiflexion in the sagittal plane and significant eversion in the coronal plane and external rotation in the axial plane at the tarsometatarsal joint. Distance mapping analysis of wave-bearing CT images identified differences in surface-to-surface interaction at the first-tarsometatarsal and medial cuneiform.

three-dimensional analysis

first-tarsometatarsal joint

weight-bearing CT scans

bunion deformity

mid-shaft first-tarsometatarsal osteotomy